Residential solar panels are often sold with long-term loans or leases, with homeowners entering contracts of 20 years or more. But how long do panels last, and how resilient are they?
Panel life depends on several factors, including climate, module type, and the racking system used, among others. While there isn’t a specific “end date” for a panel per se, loss of production over time often forces equipment retirements.
When deciding whether to keep your panel running 20-30 years in the future, or to look for an upgrade at that time, monitoring output levels is the best way to make an informed decision.
Degradation
The loss of output over time, called degradation, typically lands at about 0.5% each year, according to the National Renewable Energy Laboratory (NREL).
Manufacturers typically consider 25 to 30 years a point at which enough degradation has occurred where it may be time to consider replacing a panel. The industry standard for manufacturing warranties is 25 years on a solar module, said NREL.
Given the 0.5% benchmark annual degradation rate, a 20-year-old panel is capable of producing about 90% of its original capability.
Image: EnergySage
Panel quality can make some impact on degradation rates. NREL reports premium manufacturers like Panasonic and LG have rates of about 0.3% per year, while some brands degrade at rates as high as 0.80%. After 25 years, these premium panels could still produce 93% of their original output, and the higher-degradation example could produce 82.5%.
(Read: “Researchers assess degradation in PV systems older than 15 years“)
Image: Hunt Military Communities
A sizeable portion of degradation is attributed to a phenomenon called potential induced degradation (PID), an issue experienced by some, but not all, panels. PID occurs when the panel’s voltage potential and leakage current drive ion mobility within the module between the semiconductor material and other elements of the module, like the glass, mount, or frame. This causes the module’s power output capacity to decline, in some cases significantly.
Some manufacturers build their panels with PID-resistant materials in their glass, encapsulation, and diffusion barriers.
All panels also suffer something called light induced degradation (LID), in which panels lose efficiency within the first hours of being exposed to the sun. LID varies from panel to panel based on the quality of the crystalline silicon wafers, but usually results in a one-time, 1-3% loss in efficiency, said testing laboratory PVEL, PV Evolution Labs.
Weathering
The exposure to weather conditions is the main driver in panel degradation. Heat is a key factor in both real-time panel performance and degradation over time. Ambient heat negatively affects the performance and efficiency of electrical components, according to NREL.
By checking the manufacturer’s data sheet, a panel’s temperature coefficient can be found, which will demonstrate the panel’s ability to perform in higher temperatures.
Image: Premier Solar
The coefficient explains how much real-time efficiency is lost by each degree of Celsius increased above the standard temperature of 25 degrees Celsius. For example, a temperature coefficient of -0.353% means that for every degree Celsius above 25, 0.353% of total production capability is lost.
Heat exchange drives panel degradation through a process called thermal cycling. When it is warm, materials expand, and when the temperature lowers, they contract. This movement slowly causes microcracks to form in the panel over time, lowering output.
In its annual Module Score Card study, PVEL analyzed 36 operational solar projects in India, and found significant impacts from heat degradation. The average annual degradation of the projects landed at 1.47%, but arrays located in colder, mountainous regions degraded at nearly half that rate, at 0.7%.
Image: SunPower
Proper installation can help deal with heat related issues. Panels should be installed a few inches above the roof, so that convective air can flow beneath and cool the equipment. Light-colored materials can be used in panel construction to limit heat absorption. And components like inverters and combiners, whose performance is particularly sensitive to heat, should be located in shaded areas, suggested CED Greentech.
Wind is another weather condition that can cause some harm to solar panels. Strong wind can cause flexing of the panels, called dynamic mechanical load. This also causes microcracks in the panels, lowering output. Some racking solutions are optimized for high-wind areas, protecting the panels from strong uplift forces and limiting microcracking. Typically, the manufacturer’s datasheet will provide information on the max winds the panel is able to withstand.
The same goes for snow, which can cover panels during heavier storms, limiting output. Snow can also cause a dynamic mechanical load, degrading the panels. Typically, snow will slide off of panels, as they are slick and run warm, but in some cases a homeowner may decide to clear the snow off the panels. This must be done carefully, as scratching the glass surface of the panel would make a negative impact on output.
(Read: “Tips for keeping your rooftop solar system humming over the long term“)
Degradation is a normal, unavoidable part of a panel’s life. Proper installation, careful snow clearing, and careful panel cleaning can help with output, but ultimately, a solar panel is a technology with no moving parts, requiring very little maintenance.
Standards
To ensure a given panel is likely to live a long life and operate as planned, it must undergo standards testing for certification. Panels are subject to the International Electrotechnical Commission (IEC) testing, which apply to both mono- and polycrystalline panels.
EnergySage said panels that achieve IEC 61215 standard are tested for electrical characteristics like wet leakage currents, and insulation resistance. They under go a mechanical load test for both wind and snow, and climate tests that check for weaknesses to hot spots, UV exposure, humidity-freeze, damp heat, hail impact, and other outdoor exposure.
Image: MyGenerationEnergy
IEC 61215 also determines a panel’s performance metrics at standard test conditions, including temperature coefficient, open-circuit voltage, and maximum power output.
Also commonly seen on a panel spec sheet is the seal of Underwriters Laboratories (UL), which also provides standards and testing. UL runs climactic and aging tests, as well as the full gamut of safety tests.
Failures
Solar panel failure happens at a low rate. NREL conducted a study of over 50,000 systems installed in the United States and 4,500 globally between the years of 2000 and 2015. The study found a median failure rate of 5 panels out of 10,000 annually.
Image: PVEL
Panel failure has improved markedly over time, as it was found that system installed between 1980 and 2000 demonstrated a failure rate double the post-2000 group.
(Read: “Top solar panel brands in performance, reliability and quality“)
System downtime is rarely attributed to panel failure. In fact, a study by kWh Analytics found that 80% of all solar plant downtime is a result of failing inverters, the device that converts the panel’s DC current to usable AC. pv magazine will analyze inverter performance in the next installment of this series.
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I bought panels off a guy that had been on his roof for 20 years. I bought them to play with, they are 200 watt panels, and while I haven’t looked at them for awhile, they were top of the line when he bought them, I just can’t remember who made them. Name brand like Panasonic, etc.
Anyway, this is in the PNW. Not a lot of freezing, and not many, if any days of full sun based on their position on his roof.
When I put them in full sunlight, they were well within 10% of their original rated numbers. At $20/panel, I felt I did VERY good. And I feel the panels have held up exceptionally well. The plastic junction boxes on the back are quite weathered, but the panels themselves to the naked eye appear pristine.
Thank you for this amazing insight. I am considering solar for my small 7 units apartment building in rural Kenya.
If the panel mounting rails are not fixed all on a level plain causing some panels to slightly twist when succured.
Would this be detrimental to the life and performance.
Yours sincerely R Smith
My Solar Panels began shorting and failing after about 18 years of use and are now so bad that they will essentially all need to be replaced. Inverters started failing after around 15 years of use and both had to be replaced. I realize that I was a relatively early adaptor, but finally am disappointed in both the quality and longevity of both the panels and the inverters originally purchased in 2003. I am forced now to reinvest in both, with no support from original panel manufacturer/sale and really no support from government incentives after the initial solar equipment failed. I wonder at this… if for no other reason than the stated need in your article to replace panels due to efficiency degradation over time, the incentive program should also support ongoing solar projects that will inevitably need upgrades or maintenance/repairs. I am in the process of replacing my entire solar system with, I hope, more efficient and more robust equipment at my own cost. I will still support Solar and Wind generation going forward. But clearly these Solar systems, while largely not requiring a lot of maintenance, are not nearly as problem free or robust as I had originally hoped and believed they would be. And while I am grateful for the government initiatives and support for the original Solar investment, I feel a bit abandoned as the inevitable happens and the stuff fails. Somehow I don’t think I’m alone in this.
I was unable to find a conclusion in this article.
Where to buy the best Solar panel, Batteries, inverters (1.5 kw to 5kw), combiners and other accessories. Does rainy weather condition affect the solar panel maintenance like molds on the surface mount.
Wasn’t expecting the LID thing much, what’s that materially from? Here I thought that there would be more failure from being downrange of the Santa Ana Winds or bullets or birds who like to start beefs by dropping sabots. Or scrappers who pull live 1400 V busses.
Study not explicitly linked bc. It’s from 2017? Well, we can look forward to a few reports from KAUST or Egypt for balance, if not like, well looked after detail data from failed states with awesome jungles, and Eastern Russian States or Thai projects. No slow loris carveouts yet…
Solar panel will last it 20-30 yrs as long as they have them clean off twice a yr ,with all that dirt on solar may them work harder plus getting full sun is important ,
I notice that this article doesn’t mention dust and other debris, as a factor affecting output over time. Is this because it isn’t a significant factor or just hard to study the effects? Something I have been wondering about after noticing how significantly different my window transparency appears after washing.
I didn’t like this article because it makes such a big deal over relatively small losses. Now people will think less of used modules. That’s sad, because Solar panels are like Diamond’s they never stop being valuable, who would throw away a diamond just because of blemish or a small crack that reduced their original beauty. Nobody ! Solar panels never stop producing power. Essentially they are rocks that make beautiful electricity! What is something great about solar panels is their longevity. You made such a big deal about the small amount of power loss that you will now have fewer people wanting to buy used modules. Great now you have created more paranoia about used modules. After all your details about minute losses you helped create bigger piles of used modules that no one knows what to do with them. Nobody knows how to recycle them just like nuclear waste or used lithium ion batteries. You just made it harder to get people to reuse them even though they hardly can be considered un-useable. However I’m sure manufacturers are happy about it, as well as the State Corporation Commisioners, electric utility industry and all their lobbyists. Gee do you think it might just be about more money judt for them. Gee I wonder why you guys are on the their side to control the solar industry. We, the people, are under attack by the utility companies and their massive effort to take away the savings and the independence solar energy offers us and our kids from having any savings from any part of it . It would mean we no longer have to depend on them. Is allowing the utility companies to provide solar energy to the masses a conflict of interest ? Geeezzzz do you think so ? Really ? How ignorant can you get. In 1977 the Union of Concerned Scientists gave testimony in front of the U.S. House of Representatives’ Science and Technology Committee where they listed over 25 reasons why allowing the electric utility industry to be involved in solar energy was a clear conflict of interest. I was there. And I’m still here asking why did everyone act like, who cares?? Obviously this magazine isn’t going to point this fact out. It’s never even mentioned it. Why don’t you report on how they are sending a hoard of their lobbyists out to both sides of the legislatures in every state and to the governors themselves, to get them to vote for their bills that would give them total control of solar energy.
Enough ! I’ll probably get sued for my opinion. But America was founded by people who believed in a Declaration of Independence. But somehow solar energy is not considered an unalienable right, even though it falls freely from our Sun every single day.
Stop focusing on 1/2 a percent loss a year and focus on the reality of a 100 % loss that America is headed for, unless we stand up and fight back together.
In my job as a business owner, once a problem comes up I try to get all parties to focos on the solution not whine about how unfair it is. And so if I have your attention I would like to offer a solution for this problem we seem to be having over taking control of the immense benefits solar energy offers all the people on this incredible planet for the next few million years.
It’s very simple and the cost is very, very, low. I’ve saw how well it works in the Office of Congressman George E. Brown, Jr. George by the way was Chairman of the House Science and Technology Committee. (By the way he was the only Congressman who voted against the Vietnam War) .
If you want to help do something to solve the problems I mentioned in this comment, feel free to call me any time.
I apologize for any typos but I’m seventy two now and even though I’ve been in the solar business since I s started The Tucson Free Energy Center, my fingers have grown too fat to type my feelings and opinions up on my cell phone and since I’m too stubborn to use a lap top or a computer your stuck with them. However you get this big apology instead of me just saying “I’m sorry”. My father Bill Kimball was a judge and he told my 3 brothers and I, “Don’t say your sorry ! I hear that all day long .” Instead I have to say , “I apologize and I’ll do my best never to do that again.”
Always ask “Why Not? Never ask “Why?, it will take you a lot farther in life.” Congressman George E. Brown, Jr.